Gravel is priced by the ton but measured by volume, and the conversion depends on which stone you order. Pick the material, and add a compaction allowance if it is going down as a base.
Loose stone is awkward to measure in a truck but easy to weigh on a scale, so quarries sell by weight. You still have to think in volume, because what you are filling is a depth over an area. The conversion between the two is the density, and it is not the same for every stone.
| Material | lb per yd³ | Tons per yd³ |
|---|---|---|
| Crushed stone | 2700 | 1.35 |
| River rock | 2700 | 1.35 |
| Pea gravel | 2800 | 1.40 |
These are working averages for dry material. Wet stone weighs more, and any quarry will give you their own figure for the specific product. If you are ordering several tons, ask — a 10% density difference is a real amount of money.
A waste factor covers material you lose. Compaction is different: none of it is lost, it simply occupies less space once the air between the stones is driven out. Angular crushed stone loses roughly a fifth of its loose volume when it is properly compacted.
That is why the compaction allowance here is added rather than optional. If you order enough loose stone to fill a 4 inch void and then compact it, you end up with about 3 inches of finished driveway.
Rounded stone is the exception. Pea gravel and river rock do not interlock, so they barely compact at all — set the compaction question to no when you are spreading a loose decorative layer.
A driveway built up in two compacted lifts holds together far better than the same depth dumped and rolled once. The lower layer is usually a coarser crushed stone that locks into the subgrade; the top layer is finer and gives the surface. Run this calculator once per layer and add the results.
| Assumption | Value used |
|---|---|
| Crushed stone density | 2700 lb/yd³ |
| River rock density | 2700 lb/yd³ |
| Pea gravel density | 2800 lb/yd³ |
| Pounds per short ton | 2000 |
| Compaction allowance | 20% |
| Cubic feet per cubic yard | 27 |
Densities are averages for dry material and vary by quarry, stone size and moisture. Confirm with your supplier before ordering anything more than a few tons.